The module Foreign.Marshal.Alloc provides operations to allocate and
deallocate blocks of raw memory (i.e., unstructured chunks of memory
outside of the area maintained by the Haskell storage manager). These
memory blocks are commonly used to pass compound data structures to
foreign functions or to provide space in which compound result values
are obtained from foreign functions.

If any of the allocation functions fails, a value of nullPtr is
produced. If free or reallocBytes is applied to a memory area
that has been allocated with alloca or allocaBytes, the
behaviour is undefined. Any further access to memory areas allocated with
alloca or allocaBytes, after the computation that was passed to
the allocation function has terminated, leads to undefined behaviour. Any
further access to the memory area referenced by a pointer passed to
realloc, reallocBytes, or free entails undefined
behaviour.

All storage allocated by functions that allocate based on a size in bytes
must be sufficiently aligned for any of the basic foreign types
that fits into the newly allocated storage. All storage allocated by
functions that allocate based on a specific type must be sufficiently
aligned for that type. Array allocation routines need to obey the same
alignment constraints for each array element.

allocaBytes n f executes the computation f, passing as argument
a pointer to a temporarily allocated block of memory of n bytes.
The block of memory is sufficiently aligned for any of the basic
foreign types that fits into a memory block of the allocated size.

The memory is freed when f terminates (either normally or via an
exception), so the pointer passed to f must not be used after this.

Resize a memory area that was allocated with malloc or mallocBytes
to the size needed to store values of type b. The returned pointer
may refer to an entirely different memory area, but will be suitably
aligned to hold values of type b. The contents of the referenced
memory area will be the same as of the original pointer up to the
minimum of the original size and the size of values of type b.

Resize a memory area that was allocated with malloc or mallocBytes
to the given size. The returned pointer may refer to an entirely
different memory area, but will be sufficiently aligned for any of the
basic foreign types that fits into a memory block of the given size.
The contents of the referenced memory area will be the same as of
the original pointer up to the minimum of the original size and the
given size.